1. Technical Field
The present invention relates to a technique of analyzing atrial fibrillation.
2. Related Art
In the medical field related to heart disease, there is a technique of analyzing atrial fibrillation. JP-A-2009-89883 discloses a technique of measuring the RR interval obtained from an electrocardiogram of each beat and analyzing atrial fibrillation on the basis of the standard deviation and the frequency distribution. Hayano J, Yamasaki F, Sakata S, Okada A, Mukai S, Fujinami T “Spectral characteristics of ventricular response to atrial fibrillation” Am. J. Physiol. 1997; 273: H2811-H2816 discloses that the RR interval during atrial fibrillation is irregular, a 1/fβ component is present when the frequency analysis of cardiac beats of atrial fibrillation is performed, and a white noise pattern appears due to this variation.
In JP-A-2009-89883 and Hayano J, Yamasaki F, Sakata S, Okada A, Mukai S, Fujinami T “Spectral characteristics of ventricular response to atrial fibrillation” Am. J. Physiol. 1997; 273: H2811-H2816, it is necessary to measure the RR interval of each beat accurately for the exact analysis of atrial fibrillation. The RR interval can be measured not only from the electrocardiogram waveform signal obtained by measuring an electrocardiogram but also from the pulse wave signal obtained by measuring a pulse wave.
However, in the case of measuring the pulse wave, the subject can move freely during the measurement in many cases. Accordingly, the influence of body movement noise is likely to be included in the pulse wave signal. Also in the case of measuring the electrocardiogram, the influence of body movement noise is likely to be included in the waveform signal of the electrocardiogram although there is a difference compared with the case where the pulse wave is measured. When there is such influence of body movement noise, it is very difficult to measure the RR interval of each beat accurately.
For this reason, when the measurement of exact RR interval of each beat is a precondition as in JP-A-2009-89883 and Hayano J, Yamasaki F, Sakata S, Okada A, Mukai S, Fujinami T “Spectral characteristics of ventricular response to atrial fibrillation” Am. J. Physiol. 1997; 273: H2811-H2816, it has not been possible to analyze atrial fibrillation using a signal in which the influence of body movement noise is included. In addition, although it is known that the onset of atrial fibrillation may also be influenced by the amount of activity of the patient, the relationship between the amount of activity and the atrial fibrillation has not been fully examined since there are individual differences.